A detector for detecting electromagnetic radiation, especially for electromagnetic radiation in the GHz or THz range. The detector comprises a semiconductor structure having a 2D charge carrier layer or a quasi 2D charge carrier layer with an edge, at least first and second contacts to said charge carrier layer, said contacts being provided at said edge and being spaced apart by a distance, and a device for measuring at least one of the photocurrent between said first and second contacts, the photovoltage between said first and second contacts and the resistance between said first and second contacts. A device is provided for applying a magnetic field to said detector with a field component perpendicular to said charge carrier layer. An output signal of said measuring device provides information about at least one of the presence of electromagnetic radiation, the intensity of the incident electromagnetic radiation and the frequency of the incident electromagnetic radiation.